The present invention relates to a sheet feeding apparatus for feeding sheets in an electronic copy machine, facsimile or printer.
Many types of conventional sheet feeding apparatus are well known, such as the structure shown in FIG. 10 (see Japanese Utility Model No. 2,504,655). These are composed of the sheet supply tray 60 for stacking sheets, the pickup roller 61 for drawing out the lowermost sheet stacked on the sheet supply tray 60 by touching it, the sheet feeding roller 62 and the separation pad 63 arranged downstream of the pickup roller 61, the transport path 64, immediately downstream of the sheet feeding roller 62 that curves abruptly downward, the follower roller 66 arranged at the curved portion 65 in the aforementioned transport path 64, the transport rollers 67a and 67b arranged immediately downstream of the aforementioned follower roller 66 also acting as to resist. The aforementioned separation pad 63 resiliently presses the sheet feeding roller 62 from above to separate sheets fed by the pickup roller 61 to a single sheet therebetween with the sheet feeding roller 62. Separated sheet is fed into the inverting space 68 and the straight guide portion 69 by the sheet feeding roller 62. After being nipped by the transport rollers 67a and 67b, it is transported to the platen 70 by the transport rollers 67a and 67b. When the sheet is transported by the transport rollers 67a and 67b at the upstream of the transport path 64, the sheet is nipped by the sheet feeding roller 62 and the separation pad 63. For that reason, a large transporting resistance force is applied to the sheet being transported, but transporting resistance force is alleviated by the follower roller 66 which is arranged in the aforementioned curved portion 65 to prevent scratching of the images on the sheets or damaging of the reading images.
However, because the aforementioned sheet feeding apparatus is the type that supplies sheets from the lowermost of sheets stacked on the sheet supply tray 60, the final page of a plurality of originals is supplied, thereby leaving the first page for last, causing the problem of making it difficult to grasp the status of feeding originals. Thus, the aforementioned sheet feeding apparatus requires a configuration that arranges the sheet feeding roller 62 in an upward position and the separation pad 63 to resiliently press the sheet feeding roller 62 from below to respond to demands for a top supply type apparatus that supplies sheets beginning with the uppermost sheet of a plurality of sheets stacked on the sheet supply tray 60.
However, if the separation pad 63 is arranged below the sheet feeding roller 62, the aforementioned transport resistance force works downward to the separation pad and is directly applied, making the pressing force against the sheet feeding roller 62 inappropriate, and the separation pad itself hangs downward. In such a case, the function to separate subsequent sheets already drawn by the pickup roller 61 becomes ruined and causes the phenomenon of subsequent sheets being fed along with the sheet in transport.
Thus, an object of the present invention is to provide a sheet feeding apparatus that prevents sheet separation problems and double feedings of sheets.
In order to attain the aforementioned objective, the sheet feeding apparatus according to a first aspect of the present invention comprises sheet supply means for feeding sheets drawn out from a sheet supply tray, separating means for separating sheets drawn out from the sheet supply tray separatingly pressing against the aforementioned sheet supply means, therebetween the sheet supply means, transport means for transporting downstream sheets nipped by the aforementioned sheet supply means and the aforementioned separating means, a first transport path for guiding sheets fed from the aforementioned sheets supply means in a substantially tangential direction of the nipping point of the aforementioned sheet supply means and the aforementioned separating means, formed between the aforementioned sheet supply means and the aforementioned transport means, a transport path comprising a second transport path for guiding sheets from the aforementioned first transport path toward the aforementioned transport means after curving from the aforementioned substantially tangential direction to the aforementioned separating means, and follower rotating bodies protrudingly arranged from the aforementioned separating means in the aforementioned transport path, between the curving portion traveling from the aforementioned first transport path to the aforementioned second transport path and the aforementioned nipping point.
According to the invention so configured, by establishing a curved portion in substantially a straight line with the nipping point of the aforementioned sheet supply means and the aforementioned separating means and establishing a follower rotating bodies in the transport path between the aforementioned curved portion and the aforementioned nipping point, the follower roller receives the transport resistance force of the originals and alleviates the load on the sheet at the aforementioned curved portion, and no pulling force is generated in the separating means in the direction to separate from the sheet supply means. For that reason, there is no variation in the pressing force of the separating means, so the invention securely prevents separation problems caused by the separation means and double sheet feeds.
It is preferable to establish the aforementioned curved portion near the downstream side of the aforementioned nipping point. Doing so shortens the transporting distance from the aforementioned nipping point to the transport means thereby enabling a more compact overall transport path.
Also, it is preferable to establish in the second transport path a second curved portion that curves sheets to the transport path and in the aforementioned curved portion, to arrange a second follower rotating bodies that protrudes from the inner side of the aforementioned curved portion into the transport path. Doing so enables feeding the sheets in the appropriate direction toward the transport means and alleviates the transport force applied to the sheet.
Also, according to the present invention, it is preferable that at least one of the aforementioned sheet supply means, the follower rotating bodies and the transport means is composed of one or more rollers, and that at least one follower roller and transport roller be arranged from substantially the center of the width direction of the sheets supply roller in a straight line along the sheet transport direction. In that way, by arranging a first follower roller that alleviates the transport resistance force in a straight line tying the center position of the sheet feeding roller and the transport roller, and a second follower roller, the load applied to sheets in the aforementioned curved portion when the transport roller is transporting sheets is effectively alleviated.
It is also preferable to use the substantial center of the width direction of the aforementioned sheet feeding roller as the apex and to arrange the aforementioned follower roller on both sides of a triangle shape tying the apex and the both ends of the width direction of the transport rollers. Such a roller array is an even more effective way to alleviate the load applied to sheets in the aforementioned curved portion when sheets are transported by the transport rollers.